Anomia

Anomia is a genus of saltwater clams, marine bivalve mollusks in the family Anomiidae. They are commonly known as jingle shells because when a handful of them are shaken they make a jingling sound, though some are also known as saddle oysters.

This genus first appeared in the Permian period of China, Italy, and Pakistan. Anomia species are common in both tropical and temperate oceans and live primarily attached to rock or other shells via a calcified byssus that extends through the lower valve. Anomia shells tend to take on the surface shape of what they are attached to; thus if an Anomia is attached to a scallop shell, the shell of the Anomia will also show ribbing. The species A. colombiana has been found in the La Frontera Formation of Boyacá, Cundinamarca and Huila of Colombia.